ThermalRate™ System

Advantages

Low Cost of Installation
ThermalRate™ is inexpensive to install, since it does not require any physical modification of the line. In addition, installation never requires a line outage, since no contact with the actual conductor is required. A line outage can be very difficult to obtain because taking a line out of service reduces system reliability. Since the line is not taken out of service, there is no lost revenue during the outage. Another factor which keeps installation cost low is that ThermalRate™ Monitors (TRMs) are flexible in where they can be located, whether on an existing transmission structure, special pole, or on a mast at the substation.

Rugged
The TRM uses a patented, simple design with no delicate or moving parts to wear out. TRMs are not susceptible to damage by high wind, ice, or birds. Re-calibration is not necessary.

Ratings Can Be Calculated at Any Load Level

Tension, sag, and line temperature rating methods require that the line be carrying significant current for the method to work. At low loading, these methods, which are quite similar, are not able to determine the rating. The line load needs to be above about 1 amp per mm2 (35-40% of the static rating) before the conductor has enough change in temperature/sag/tension for the ratings to be able to be determined.

Consider 115 kV lines in "parallel" with a 345 kV backbone. The 115 kV lines are normally lightly loaded, but during a loss of the 345 kV line, the 115 kV lines carry the load of the 345 kV line. This scenario is common. While the normal load of the 115 kV lines is low, the operator needs to know their rating in the event of a contingency. The TRMs work equally well in low- or high-load conditions and work well for this scenario.

Direct Method of Determining Rating
Since the TRM use a replica of the line, it responds to weather conditions as the line does. The nature of the design takes into consideration difficult measurements such as highly variable winds in speed and/or direction (turbulent); wind that has some vertical component, fog, or rain; reflected sun off the ground or clouds; humidity; clear sky radiation; and the time constant of the conductor. These are all accounted for inherently and are reflected in the temperatures of the Sensor.

ThermalRate™ Gains Time for the Utility
There is uncertainty in new generation coming on-line and related uncertainty in line loading due to open access laws. ThermalRate™ is a small investment, which can be installed to safely operate the line until it can be decided if a new line is really required in a certain location. A new line can take years to get built, and ThermalRate™ gains the utility some time for continued safe operations of the existing line.

Wind Farm Application
ThermalRate™ can be an ideal solution for transmission lines connecting wind farms to the grid. When the wind is high, more power is generated, and the rating is also high. Therefore, when the capacity is needed, ThermalRate™ will show that it is available.
North American Wind Power article showing the benefit of dynamic rating for wind generation.

River Crossing Application
River crossings can limit the entire line, since they are so long and sag more than shorter spans. A TRM installed at one of the two ends of the span can accurately determine the true rating for the span.